Middle Fork of The American RiverField Assignment

John ForsProfessor LawlerGEL 104, Summer 2011July 10, 2011

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Content Background & Method Brief Geological History River Canyon Geology Gold Deposits Rock Examples Geological Features Plant Examples

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Background and Research Methodology In late June I visited an area in the canyon of the

Middle Fork of the American River The photos and rock samples included in this

report are from this field trip 3D map images were prepared using Google Earth Identification of rocks done using: Geology of the

Sierra Nevada, by Mary Hill (2006) Identification of plants done using: Trees and

shrubs of California, by Stuart & Sawyer (2001)

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Site Location

Near Auburn, California

Entry through Driver’s Flat Road, on dirt road down to bottom of river canyon

Coordinates 38.962362,-120.929775

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Deep Down in the River Canyon

View up the very deep canyon of Middle Fork of American RiverValley has been carved by the flow of the river for last several million years

Google Earth

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Quick Geological History and Overview Sierra Nevada is a tilted fault block 400 miles long,

with rugged east face, and sloping west face West side has metamorphic rock formed by plate

tectonics in Early Paleozoic to Late Jurassic (400-120 million years ago) – with portions of ancient seafloor

Volcanic eruptions filled ancient valleys with lava and mudflows

Present river system formed by erosion during last 5 million years

(Lindstrom, 2000; “North,” 2006; “North,” 2007)

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Geology of Middle Fork River Canyon Undulating steep mountains, elevation 1,600 –

5,600 feet Foresthill Divide is a NE trending ridge system,

separating North and Middle Forks of American River

River has cut steep canyons 1000 ft below top of Foresthill Divide

Significant surface erosion, especially on steep hill sides

Mean annual precipitation between 30-40 inches Extremely low seismic activity

(“North,” 2006; “North,” 2007)

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Gold Deposits Around Foresthill Area Streams flowing down western slopes carried

Auriferous gravels Auriferous gravel <0.5 percent of soil types in the area Flows of lava later covered and protected many of

these deposits Gold veins usually are 3-4 feet thick, in NW direction Gold discovered in Foresthill in 1850 Primarily placer mines, with extensive hydraulic mining In next 15 years more than $10 million was extracted

(“Description,”1897; “Gold,” 1970; “North,” 2006; “North,” 2007)

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Rock Sample: Periodotite / Serpentinite

Serpentinite is derived from basic intrusive rock

It is created through geological low-temperature metamorphic process involving heat in presence of water

Peridotite is derived from the Earth's mantle

Description: some small grains, black/gray color, can be scratched, no layers, can be fractured

Identification: I believe this is Serpentinite, a plutonic igneous rock type

(Hill, 2006)

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Rock Sample: Greenstone /Green schist

Description: weathered red/brown color, fine-grained, can be scratched, faint layering

Identification: I believe this is Greenstone, a metamorphic rock

The rock is derived from basalt, gabbro or similar rocks containing sodium-rich plagioclase feldspar, chlorite, epidote and quartz

Greenstone and green schist belts are primarily formed of fine-grained volcanic rocks, dominated by basalt, with minor parts sedimentary rocks

(Hill, 2006)

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Sandstone Rock Outcropping Fragile grainy sand-colored

sedimentary rock Appears to be sandstone or

gritstone The outer layer, in part, is

held together by a thin layer of vegetation

Likely result of earlier deposits of sand, later put under high pressure from overlaying sediment or lava layers

Tilted almost 90 degrees, by earlier rock folding process

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Polished Bedrock Down at River Level Sections of the rock

at river level has smooth appearance

Polishing effect likely is from flowing silt-filled water

It is difficult to see what the rock type is since the surface is so changed. It could either be the from the intruding plutonic rocks, or from the older sedimentary rocks from older sea bottom

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Erosion and Break Up of Larger Rocks

Large boulders cracking and fragment into smaller blocks Process driven by heating/freezing cycles, as well as

erosion from water, snow, and ice The large boulder may have come down by rock fall from

higher up in the river canyon as part of ongoing erosion

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Tilted Sedimentary Rocks Appears to be layered sedimentary rock Could be part of the earlier seabed Tilted between 60 to 90 degrees, mostly

facing NE Covered by moss and other plants

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Plant and Animal Life Ground around

the river bed is mostly rocky and dry

Mixed forest, oaks, and small shrubs; with habitat for diverse fauna

No major animals seen, except one river otter (which quickly disappeared under the surface)

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Madrone Tree

I believe this tree is a Pacific Madrone (Arbutus menziesii)

(Stuart & Sawyer, 2001)

• The madrone is a member of the Heath family (Ericaceae) of vascular green plants• Ericaceae is under the order Ericales, which evolved from Magnoliales,  which in turn descended from angiosperms originating in the Mesozoic Era• It has high tolerance to poor soil, drought, extreme temperature, shade, and elevation; which enables it to thrive in many different habitats

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Evolution of Pacific Madrone (Arbutus menziesii) Plantae => Angiosperms => Eudicots => Asterids =>

Ericales => Ericaceae => Arbutus => A. menziesii

Fossilized leaves of a species similar to modern day Pacific Madrone have been found in northwestern Nevada, the Blue Mountains of Oregon, and Tuolumne County, CA This species dates to the Miocene Epoch of 12 to 26 million

years ago The species composition and flora is similar to oak-madrone

forests in California today Current madrone-related flora is believed to have originated

in southwestern North America

(Axelrod, 1958;Tappeiner & McDonald, n.d.)

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Oak Tree

I believe this tree is a Canyon Live Oak (Quercus chrysolepis)

(Stuart & Sawyer, 2001)

An evergreen oak that is found in the southwestern part of North America, especially in California Coast Ranges

Often found near creeks and drainages, growing in moist cool microhabitats

It is part of order Fagales, also descendant from angiosperms

May live for up to 300 yrs

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Evolution of Canyon Live Oak (Quercus chrysolepis) Plantae => Angiosperms => Eudicots => Rosids => Fagales

=> Fagaceae => Quercus => Protobalanus => Q. chrysolepis

Early fossil evidence of family Fagaceae found in western Tennessee, dated to Paleocene/Eocene boundary (Crepet & Nixon,1989)

Quercus forms swarms of hybrids making precise analysis of lineage difficult

More than 200 different species of Quercus across every continent of the world, including 89 in the US, and 20 in California

Quercus in general are wind-pollinated, however, Lithocarpus and Chrysolepis are insect-pollinated, thus causes major differences in their flowers

Chrysolepis the most common member of Protobalanus group in California

(Crepet & Nixon,1989; Nixon, 2002)

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Flowering Manzanita Shrub

I believe this shrub is a Mexican Manzanita (Arctostaphylos pungens)

Belong to order Ericales(Axelrod, 1958; Stuart & Sawyer, 2001)

About 60 species of Arctostaphylos, ranging from ground-hugging arctic, coastal, and mountain species to small trees up to 6 m tall

Believed to have come from subtropical to warm temperate groups and then evolved in response to the expansion of a new adaptive zone: dry climate

Also from angiosperms

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Evolution of Mexican Manzanita (Arctostaphylos pungens) Plantae => Angiosperms => Eudicots => Asterids => Ericales

=> Ericaceae => Arctostaphylos => A. pungens

Shares evolutionary history with Pacific Madrone (Arbutus menziesii) as described on earlier pages

Rich fossil record, and considered to be of Miocene origin, approx 15 million years ago

Radiation of genus occurred 1.5 million years ago during the Pleistocene

Oldest remains of Arctostaphylos from lower Pliocene Texas (Adams,1935)

Southern California thought to have been a major Pleistocene center of distribution and variation, which then shifted northward (Adams, 1935)

(Adams, 1935; Markos,1995)

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Evolutionary Tree of Angiosperms

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ReferencesAdams, J. E. (1935). A systematic study of the genus Arctostaphylos. Berkeley Press: Berkeley.

Axelrod, D. (1958). Evolution of the madro-tertiary geoflora. The Botanical Review. 24(7) 433-509.

Crepet, W., Nixon, K. (1989). Earliest megafossil evidence of Fagaceae: phylogenetic and biogeographic implications. American Journal of Botany. 76:

842-855.

Description of the Gold Belt. (1897). pubs.usgs.gov. Retrieved July 7, 2011, from pubs.usgs.gov/gf/041/text.pdf

Gold Districts of California. (1970). Oakland Museum of California. Retrieved July 8, 2011, from http://museumca.org/goldrush/dist-foresthill.html

Hill, M. (2006). Geology of the Sierra Nevada (Rev. ed.). Berkeley: University of California Press.

Lindstrom, S. (2000, July 15). FORESTHILL DIVIDE COMMUNITY PLAN (FDCP) HERITAGE RESOURCE ELEMENT. Appendix B.1. Retrieved July

7, 2011, from http://www.placer.ca.gov/Departments/CommunityDevelopment/Planning/CommPlans/FDCP/~/media/cdr/Planning/CommPlans/

FDCP/RDEIR/Appendices/deir%20rfdcp%20appendix%20b%201.ashx

Nixon, K. (2002). The Oak (Quercus) Biodiversity of California and Adjacent Regions1. US Forest Service. Retrieved July 10, 2011, from

www.fs.fed.us/psw/publications/documents/psw_gtr184/psw_gtr184_001_Nixon.pdf

North Fork American River Trail. (2006, June 1). Welcome to Beautiful Placer County California. The official website.. Retrieved July 8, 2011, from

http://www.placer.ca.gov/Departments/CommunityDevelopment/EnvCoordSvcs/EIR/NorthForkTrail.aspx

North Fork/Middle Fork American River Sediment Study. (2007, April 1). USDA. Retrieved July 7, 2011, from

www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5275882.pdf

Stuart, J. D., & Sawyer, J. O. (2001). Trees and shrubs of California . Berkeley: University of California Press.

Tappeiner, J. C., & McDonald, P. M. (n.d.). Arbutusmenz. Northeastern Area State & Private Forestry - USDA Forest Service. Retrieved July 10, 2011, from

http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/arbutus/menziesii.htm